Various body pigments are blended with cosmetics with the aim of improving the extensibility, adherence, hiding power, moldability, etc., of products. As the body pigment, there can be mentioned inorganic powder such as talc, kaolin, and mica and organic powder such as nylon powder, polyethylene powder, polystyrene powder, acrylic resin powder and epoxy resin powder. Among them, mica has been used frequently since it has an excellent transparent feeling, gloss and extensible feeling upon use. Recently, synthetic mica has been developed in addition to natural mica.
Synthetic mica is a phyllosilicate mineral obtained by a melting method, hydrothermal method or intersolid reaction method. Synthetic mica powder composed of good crystals has been prepared by mixing compounds each containing potassium, sodium, magnesium, aluminum, silicon and fluorine at a predetermined ratio, melting, crystallizing, cooling, and then mechanically pulverizing them. Such synthetic mica can include, for example, as below:
KMg.sub.3 (AlSi.sub.3 O.sub.10)F.sub.2 potassium phlogopite PA1 KMg.sub.2 1/2(Si.sub.4 O.sub.10)F.sub.2 potassium tetrasilicon mica PA1 KMg.sub.2 Li(Si.sub.4 O.sub.10)F.sub.2 potassium taeniolite PA1 K2/3Mg.sub.2 1/3Li2/3(Si.sub.4 O.sub.10)F.sub.2 PA1 NaMg.sub.3 (AlSi.sub.3 O.sub.10)F.sub.2 sodium phlogopite PA1 NaMg.sub.2 Li(Si.sub.4 O.sub.10)F.sub.2 sodium taeniolite PA1 NaMg.sub.2 1/2(Si.sub.4 O.sub.10)F.sub.2 sodium tetrasilicon mica PA1 Na1/3Mg.sub.2 2/3Li1/3(Si.sub.4 O.sub.10)F.sub.2 sodium hectorite
As has been described above, although the mica has excellent properties, natural mica shows a slight coloration since it contains a slight amount of metallic impurities. Accordingly, when the natural mica is blended with cosmetics, it tends to reduce the chroma of the outer looking color of the cosmetics. While organic pigments are used as an example of general means for improving the chroma of the outer looking color of the cosmetics, the organic pigment is poor in light stability, and degraded by the light thereby causing undesirable phenomenon as cosmetics such as discoloration or a bad odor.
Further, the mica has strong activity at the surface of powder, which tends to cause degradation in oils and perfumes.
In view of the extensible feeling upon use, spherical resin powder may be used as a substitute to some extent but, if the spherical resin powder is blended in a great amount, it reduces the adherence of cosmetics to skin and, further, worsens the moldability of cosmetics.
Referring to the gloss, while may one consider blending titanium-mica type pearl pigment instead of mica, it also worsens the moldability of cosmetics.
In short, while mica has excellent properties that can not be substituted with other powders, optional blending thereof is inhibited at present in view of the coloration due to a slight amount of metals and surface activity.
Furthermore, mica has a drawback when blended with cosmetics that it is poor in oleophilicity, poor in dispersion stability and incapability of satisfying smooth feeling upon use.
That is, although the natural mica has excellent properties that can not be substituted with other powders, it involves a problem of coloration due to the slight amount of metallic impurities, the problem of surface activity and the problem of diffusion into the substrate, which inhibits the optional blending.
With an aim of overcoming such problems, the synthetic mica has been produced as described above. Since there is no incorporation of a slight amount of metallic impurities in the synthetic mica, the problem of reducing the chroma of the outer-looking color of the cosmetics can be overcome. However, the activity at the surface of the powder is high as in the case of the natural mica. In addition, since fluorine ions (F.sup.-) are leached out when blended in the cosmetic preparations, there is a safety problem. Furthermore, the oleophilicity is at the same level as the natural mica and the dispersion property or feeling upon use can not be improved.
In view of the above, it has keenly been demanded for the development of synthetic mica capable of suppressing the surface activity, with no leaching of fluorine ions and excellent in the dispersion property and feeling upon use, for the aim of producing cosmetics, particularly, make-up cosmetics excellent in extensibility, gloss, adherence and moldability, providing an outer looking color at high chroma, and high stability and safety.
For overcoming these problems, the present inventors have tried regarding the mol number of F as follows:
(1) A method of dissolving F with strong acid.
(2) A method of synthesizing while decreasing the blending amount of F upon melting.
(3) A method of repeating washing with purified water, boiled water, etc.
However, not only F but also Mg, K, etc., are leached out in the same way to possibly destroy the structure in the method (1). Only the deposition amount of mica crystals is decreased and the mol number of F in the synthetic mica does not change in the method (2). No substantial effect can be obtained for the decrease of the mol number of F by the method (3).
For improving the oleophilicity, it has been considered to improve the hold of oils by making the surface shape of the synthetic mica particles more irregular and there have been tried those methods of vibration treatment using supersonic waves, chemical treatment using an oxidizing or reducing agent and treating with strong alkali. However, none of the methods has been effective and, rather, undesirably resulted in coarse powder due to secondary coagulation, etc.